Behold the Mighty Trigger Point

Some clinicians are still endeavouring to prove that myofascial pain is a distinct localised clinical entity attributable to “trigger points” (TrPs) within muscles if not also other soft tissues.

There are others who continue to propose that the pain of FMS (fibromyalgia syndrome) “is largely composed of pain arising, at least partially, from TrPs” [Fernández-de-Las-Penãs & Arendt-Nielsen 2016].

It might seem therefore that myofascial pain syndrome (MPS) and FMS are two sides of the TrP coin, the label used dependent upon which side the coin lands. If only those TrPs could be treated!

Recently Kumbhare et al. [2017] reviewed the very limited literature that in their opinion justifies the use of ultrasound-guided injection techniques in the treatment of patients in whom “trigger points” are thought to be the cause of their pain. Have they found the ultimate solution?

The significant problems that bedevil this article quickly become evident from an analysis of the opening sentences:

Myofascial pain syndrome (MPS) is a common regional musculoskeletal pain syndrome that can cause local or referred pain. In other words, a pain syndrome is said to cause itself, which is of course a logical impossibility!

The authors then appear to accept the existence of pathophysiological entities for which there is no evidence: It [MPS] is characterized by myofascial trigger points (MTrPs), which are hard, palpable discrete localized nodules located within taut bands of skeletal muscle and can be painful on compression. However, such nodules have never been objectively demonstrated – histologically, ultrastructurally, biochemically or electrically. So how can it be known that they are the primary cause of musculoskeletal pain?

To be fair, the authors do point out that diagnosis is difficult, not least because palpation is unreliable and there are no accepted standardised clinical criteria for the diagnosis of MTrPs. Yet Khumbare et al. [2017] advise clinicians to rely on palpation to detect taut bands in muscle prior to applying the ultrasound probe to these regions. To find what? Some studies report finding hypoechoic regions, whereas others report the regions of interest to be hyperechoic. Elsewhere in the article the authors favour the former possibility but provide no reason for this choice.

Milton Cohen

So, what is the “gold standard” for the identification of a phantom? And if, as the authors concede, there are no data on inter-rater reliability when using ultrasonography and no consensus within the literature on what can be identified, how can they logically – let alone ethically – recommend injection therapy?

The only valid conclusion that can be drawn from this article is that the authors are locked into a bogus construct about which they are hopelessly confused [Quintner & Cohen 2015; Quintner et al. 2015].

In a tantalizingly titled editorial, Finlayson [2017] warns those who insert needles into targeted points deeper than 2 cm, or adjacent to vulnerable soft tissue structures such as the lung (and major blood vessels), that pneumothoraces related to such injections are a major cause of litigation in the field of chronic pain. He suggests that there is an important role for ultrasound guidance to avoid such complications.

As for the use of ultrasound for diagnostic purposes, he recommends that “further research is required to determine the clinical value of sonographic changes associated with MTrPs, as well as the reliability with which they can be detected.”

Where does this leave the practice of blind “dry needling”? The answer lies in the title of the editorial – Fool’s Gold.

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